The invention relates to a valve with a housing in which is arranged rotatably moveably between two bearing sleeves with bearing surfaces, which are, for example, shaped like segments of a sphere, a generally spherical closure part, and with a passage, passing through the closure part, for a liquid or gaseous medium.
In known valves of this type the closure part mostly has a complete spherical shape. The passage passing through the latter is formed by a bore leading through the centre point of the sphere, which bore runs radially to the axis of rotation. By rotation of the spherical closure part about this axis of rotation, the ends of the bore are brought into coincidence with the centre openings of the bearing sleeves, if the valve is to be opened. In the closed position the bore lies approximately at right-angles to the centre axis of the bearing sleeve arranged coaxially with respect to each other.
It is appropriate in many instances, e.g. to relieve in the disconnected state, a compressed air line connected to such a valve. If the valve is connected on the inlet side to a compressed air supply, thus, for example to a compressor, and a compressed air tool is connected to the outlet side of the valve, then it has to be taken into account after the shut off that the line leading from the valve to the compressed air tool is still under pressure. In this case it is at least dangerous to separate the compressed air tool from its line connection, since the pressure still prevalent in the line can suddenly force the connection ends apart immediately after the release of a coupling holding the latter together. This possibility is not taken into account in many instances when releasing the coupling. However, the pressure can also still be so large that the release of the coupling is made difficult or is made impossible.
In order to avoid these disadvantages and difficulties, it would be appropriate if, in the closed position of such a valve, a relief of pressure in the line leading to the compressed air load could also simultaneously take place. However, there is still no valve, with a spherical closure part with which such a relief is possible.
Indeed, it is known in the case of valves of different construction to achieve such a relief of pressure, that is to say in the case of a valve the closure member of which is constructed with a shape like a truncated cone. The tapered outer surfaces of this closure member abut at corresponding internal surfaces of the valve body, wherein between these surfaces a particularly accurate fit is necessary in order to achieve a sealing effect which is as good as possible. However, it is very difficult to achieve an absolute and reliable sealing effect in the case of these valves. This is primarily due to the particularly high requirements which are made of the production accuracy. In addition however, grooves or channels, which considerably reduce the sealing effect, are easily formed at the tapered sealing surfaces in the course of use. The grooves or channels again already result due to small foreign or dirt bodies, the penetration of which into the interior of the valve is mostly unavoidable.
As compared to this, valves of the type named at the outset with a generally spherical closure member can be very reliably sealed, since the bearing sleeves comprise material which is particularly suited herefor, the elasticity of which ensures every time a good abutment against the seal surfaces of the closure member.